I think it would generally make sense to store these 3 values in the device structure. On Windows we would have to use the values InputReportByteLength, OutputReportByteLength and FeatureReportByteLength from https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/hidpi/ns-hidpi-_hidp_caps . On all other backends we could use your parser to determine them - and with the testcase you proved that they are the same as on Windows.
In this way, we were able to programmatically determine the required buffer sizes for read/write operations on all platforms.

Originally posted by @JoergAtGithub in #728 (comment)

Need to consider if this is required.